Process of plating glass fiber rovings with iron metal



Dec. 31, 1957 H. R. NACK ETAL 2,818,351

PROCESS OF PLATING GLASS FIBER ROVINGS wrra IRON METAL Filed Dec. 9, 1952 INVENTOR. 1' HERMAN R NACK BY JOHN B. Wl-LEACRE MM MLW m ATTORNEYS United States Patent l 2,818,351 PROCESS OF PLATING GLASS FIBER ROVINGS WITH IRON METAL Herman R. Nack, Troy, and John R. Whitacre, Dayton,

Ohio, assignors to The Commonwealth Engineering gfirnpany of Ohio, Dayton, Ohio, a corporation of to Application December 9, 1952, Serial N 0. 324,961 2 Claims. (Cl. 117107) This invention relates to a. method and apparatus for the deposition of iron coats on strands of glass fiber. More particularly the invention relates to the iron coating of rovings of glass fiber.

In co-pending application Serial No. 298,828, filed May 24, 1952, now U. S. Patent No. 2,749,255, inventors Herman R. Nack and Howard J. Homer, and assigned to the same assignee as the present invention, there is described a method of coating rovings with metals such as nickel, copper, molybdenum and chromium. It has now been found that while well suited to those metals, the method described therein may be materially improved and rendered particularly satisfactory for the coating of rovings of glass fibers with iron by the practice of the method described hereinafter.

Rovings consist in general of a multiple of straight, that is, untwisted strands, each strand comprising a very large number of glass filaments. Thus in one roving there are eight strands and each strand consists of approximately 204 closely associated filaments; thus in the roving there are about 1632 filaments of very small diameter, that is, about microns each. Due to this very large number of filaments in close contact the application of metallic coatings to the rovings afiords considerable difficulty particularly where the coating must provide a path of relatively good electrical conductivity, as only slight discontinuity in the coating will thus increase the resistance of the article materially.

Iron pentacarbonyl is a relatively high boiling (218 F.) monometallic carbonyl, a liquid of amber-yellow coloration. The relatively low vapor pressure of the liquid in contrast to other metal bearing compounds, that is, nickel carbonylB. P. 44 C. (6.6 F.)-requires that the iron pentacarbonyl be particularly handled in order to assure of adequate and uniform metal deposition. This is particularly true where the material to be plated is of a non-metallic character.

Accordingly it is a primary object of this invention to describe a novel method of coating a glass fiber roving with iron deposited from the vapor state.

It is an important object of this invention to describe a method of coating flexible fiber glass strands with iron, which method results in a product of high flexibility.

It is another object of this invention to provide a method capable of producing iron coated glass fiber strands at high speeds.

It is a particular object of this invention to describe a novel gas plating heating arrangement.

Yet another object of this invention is to describe novel gas plating apparatus capable of coating a glass fiber strand or strands with iron at high feet per minute s eed.

These and other allied objectives of the invention are attained generally speaking by providing for the heating of the glass fiber strand or strands to the decomposition temperature of an iron bearing heat decomposable gaseous compound and vibrating the heated strand in an atmosphere of the gaseous compound to attain a uniform deposition of iron on each of the glass filaments comprising the strand. The imparting of a mechanical vibration to the strand spreads the filaments thereof and allows the gas to contact the filament surface intimately and uniformly. in this connection it is to 2,818,351 Patented Dec. 31, 1957 be noted that the heavy strands separate from each other rather readily but the filaments comprising each strand spread with more dilficulty, although under the operating conditions noted hereinafter suflicient motion is attained by each filament to free it temporarily of contact with all others, thus permitting the gas to deposit iron uniformly on the filament surface. However, upon removal of the vibratory motion the filaments readily compact and the strands reform to substantially a condition of unmetalized state.

The vibratory movement is preferably attained by drawing the material to be coated through the gas plating chamber in a slightly taut condition and then applying to the taut material a repetitive impulse which sets the strand into motion. The motion imparted is preferably as vigorous as the filamentary material will permit, for as the motion is increased the degree of spreading of the filaments increases, permitting rapid drawing of the strands through the plating area, thus enabling the achievement of high production speeds. While the speed of drawing is effected by other factors, such as the plating conditions, including the concentration of the metal bearing gas and the temperature of the roving, it may be stated generally that a drawing speed of 1 foot to 300 feet per minute is readily attained by the process and apparatus of this invention. Also the frequency of the impulses per minute applied to the moving roving is preferably relatively high and frequencies of 500 to 1750 impulses have been generally employed, although lower impulse rates may be utilized, and the invention is not to be considered as limited to the preferred stated range.

The plating conditions are in themselves not to be considered as critical. It is of course necessary that the material constituting the roving be heated to at least the minimum temperature of decomposition required for the metal bearing gas employed. It is also preferable that the plating gas flow counter-current to the moving heated roving, for the roving will be lowered slightly in temperature by contact with the cooled gas, and under this counter-current flow condition the roving will have attained a slight coating of iron before much cooling occurs. In this slightly coated condition further deposition of iron is rendered more easy and where desired a slight deposit may be inductively heated to compensate for any temperature losses. However, this factor is only important where the operating conditions, particularly temperature, closely approach marginal conditions.

As noted the heating of the iron carbonyl to elfect vaporization is an important consideration and is effected in accordance with the precepts of this invention by positioning the chamber containing the carbonyl within a vessel through which heated air is moving; preferably also a carrier gas such as carbon dioxide is employed to assist the vaporization, and this carrier may be warmed in the apparatus of this invention in its passage to the carbonyl. Thus the invention embraces within its confines apparatus particularly suitable for iron carbonyl decomposition to the metallic state.

The operating pressures for the operation of plating may vary over wide ranges from the subatmospheric to the atmospheric, but it is generally preferred to employ substantially atmospheric plating pressures, as operation under this condition permits the use of relatively simple apparatus. For example, the use of complicated scaling for the plating chamber is avoided.

However caution must be exercised to exclude the oxygen and water vapor of the air particularly since under alkaline conditions iron pentacarbonyl reacts with water to set hydrogen free. This hydrogen may then combine with iron carbonyl to form a hydride. The alkali which 3 promotes this reaction is present on the surface of most glasses to such an extent as to require caution to preclude the possibility of such reaction.

The invention will be more fully understood by reference to the following detailed description and accompanying drawing wherein the single figure illustrates schematically the apparatus useful in the process.

Referring to the drawing there is shown at 1 a cylinder containing carbon dioxide under pressure, the cylinder being equipped with a valve 2 and a gauge 3 for indicating the flow of gases through a line 5 terminating in a coil '7 as at 9. Secured to the upper end of the coil 7 is an exit conduit 11 having a check valve 12 and terminating in a U-shaped conduit member 13.

A gas plating chamber 17 is secured to the other end of line 15 and is itself provided with a gas outlet 19 and longitudinally opposed openings 21, 23: for the passage of a substantially continuous length of roving of glass fibers 24.

A tubular heater 25 is connected through opening 21 for heating of the glass fiber in its passage to the plating chamber. Chamber 17 is itself surrounded by an induction heating coil 29 which maintains the same sufiiciently hot during the plating operation to provide a gaseous atmosphere of the carbonyl; this heater also maintains the temperature of the glass fiber roving sufficiently highby radiationto insure of thermal decomposition of the carbonyl when it contacts the glass.

At the opening 23 of chamber 17 (left hand end) a casing 31 houses a shaft 33 carrying an eccentric 35 driven through a mechanism (not shown). The eccentric 35 in the course of its revolutions contacts the roving Z4 setting the same into rapid vibration over the free length thereof thereby causing the same to open up into strands, and the strands into filaments, to expose the roving quite completely to the atmosphere of the chamber 17. The filaments and strands, after plating, in their passage through seal 37 reconverge to their original form. A similar vibration apparatus is described in the copending application referred to hereinbefore.

Seal 37 consists merely of a chamber of metal or heavy rubber having an outlet 39 for the passage of roving 24 and an inlet line 41 for the passage of a carrier or other gas such as carbon dioxide from a suitable source 43. The flow of, for example carbon dioxide, is regulated by hand valve 45 adjacent gage 47 to provide a sufficient quantity of gas at 37 and 31 to prevent any carbonyl flow thereto. Thus the carbon dioxide will itself flow whether or not vacuo conditions obtain with the plating gas to chamber 17. A second and similar gas seal it) is indicated generally at the right hand of heater tube 25 and prevents air from being drawn into the system.

The gases flowing from chamber 17 may be exhausted under the influence of vacuum through outlet line 19 which terminates in a condensing coil 49 immersed in Dry Ice or other refrigerant 50. The condenser coil is provided with a return line 51 through which liquid iron pentacarbonyl may flow to lines 11 and 13 for recycling to the plating chamber. The pressure of the gases in coil 4-9 as they are being drawn therethrough will tend to force the liquid carbonyl in line 51 through check valve 52 which prevents gas flow to the coil from the source. When operated at atmospheric pressure some exhaust gases may be recycled but this is not detrimental.

The condensing coil 49 is also connected by conduit 53 with a trap 55, immersed in the refrigerant as Dry Ice 57, the trap preferably having a vacuum pump 59 at the exit thereof. Gases passing from the pump are preferably burned to remove all danger which may exist from a heavy carbon monoxide concentration. It is to be noted that vacuum conditions are not vital and that a sufiicient fiow of carbon dioxide or other carrier gas may be maintained to continually force the gases through the apparatus. The trap 55 is a safety measure for the collection of car- 4 bonyl which may possibly be carried with the exhaust gases through coil 49.

A feature of the case involves the provision of vessel 61 which houses plating chamber 17, the conduit 13 including the iron pentacarbonyl and coil 7. The vessel is provided with an inlet line 63 and an outlet 65 for the passage of dry heated air. This air surrounds and contacts the noted members thus providing an atmosphere which assists maintenance of uniform temperature conditions over the apparatus. The leads to the induction heater, the drive means for the eccentric, and the various piping arrangements may be passed through the vessel walls in sealed relation therewith in any suitable manner, the same not being critical since the air temperature Within the vessel will be about 150 P. which is sufficient however to assist in attaining a high vapor pressure of the pentacarbonyl which boils at about 218 F.

The plated roving 24 in its exit from the plating chamber will also be benefited by the heat within vessel 61 since the temperature drop of the iron-coated fibers will be more gradual and thermal shock is thus avoided.

The untreatedroving 24 is wound on a reel supported as at 67 and is initially passed through the apparatus in any suitable manner as by attachment to a tail. The plated material exiting from chamber 61 is Wound on reel 69 fastened to a support 71 in any suitable manner by a bracket as at 73. Motor 75 having a pulley 77 over belt 79 drives the reel 69 to supply the motive power for the passage of the roving through the apparatus.

In the operation of the device it is preferable to first string the roving between the reels and then to raise the air temperature of the vessel 61 While heating chamber 17; the vacuum is then applied while feeding a flow of carbon dioxide from source 43 and the chamber 15 is thus rapidly exhausted of all air, and the gas seals at 39 and 40 will prevent further air passage thereto. Under the influence of the heated air in vessel 61 an appreciable vapor pressure of iron pentacarbonyl will have developed in conduit 13 and carbon dioxide from tank 1 heated in coil '7 is passed over the carbonyl to sweep the gases to the heated plating chamber.

Motor 75 is then started to cause the roving to move leftwise in the figure and at about the same time eccentric 35 is actuated through its drive means to cause the roving to vibrate and spread out to expose the filaments to the iron-bearing gas.

When the mixture of carbonyl and carbon dioxide carrier contacts the heated glass thermal decomposition of the iron on the filaments occurs and the gaseous products of decomposition flow on to coil 49. The amount of metal deposited varies with the volume concentration and time of flow of the carbonyl gas, the speed of the roving (1-300 feet per minute) and the various conditions may be regulated to produce any desired thickness of coating.

t is generally desirable to deposit a film having a thickness which Will yield varying degrees of electrical conductivity without materially affecting the flexibility of the roving. Thus an electrical resistance of about ohms per inch was obtained from a glass having substantially infinite resistance with the following conditionsall gas flow being measured at atmospheric pressure and room temperature75 F.

Example I Carbon dioxide flow through carbonyl saturator (13) Carbon dioxide flow through gas seal (37) 2 liters per minute.

0.5 liter per minute.

Fiber speed 40 ft. per minute. Carbonyl recycling condenser (49) 32 F. Dry Ice trap (55) 70 F.

The above example clearly illustrates that the glass rovings may be well covered with the iron from the pentacarbonyl under the conditions set forth.

The example is set out as indicative only of the means of the application of the iron and is not to be considered as limitative of the invention.

It will be understood that this invention is susceptible to modification in order to adopt it to diiferent usages and conditions and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

We claim:

1. In a process of plating glass fiber rovings with iron metal as the same is passed through a plating chamber which process comprises moving the glass fiber in the form of untwisted parallel strands into a confined zone filled with dry air heated to at least 150 F., and thence through a plating area surrounded by said confined zone, excluding oxygen and water vapor from the plating area by filling the same with dry inert gas, introducing gaseous iron pentacarbonyl into said plating area together with said inert gas as a carrier, vibrating the roving to cause temporary separation of the roving strands exposing the same to gaseous iron carbonyl, and heating the thus exposed strands of glass fiber at a temperature to cause decomposition of the iron carbonyl and deposition of metallic iron on the surface of the fibers, and thereafter gradually cooling the resultant iron-coated glass fibers within said confined zone.

2. In a process of plating glass fiber rovings with iron metal as the same is passed through a plating chamber which process comprises moving the glass fiber in the form of untwisted parallel strands into a confined zone filled with dry air heated to at least 150 F., and thence through a plating area surrounded by said confined zone excluding oxygen and water vapor from the plating area by filling the same with dry inert gas, introducing gaseous iron pentacarbonyl into said plating area together with said inert gas as a carrier, vibrating the roving to cause temporary separation of the roving strands exposing the same to gaseous iron carbonyl, and heating the thus exposed strands of glass fiber at a temperature to cause decomposition of the iron carbonyl and deposition of metallic iron on the surface of the fibers, and thereafter gradually cooling the resultant iron-coated glass fibers within said confined zone, said roving strands being vibrated at frequencies between about 500 and 1750 cycles per second to cause temporary separation of the roving strands into filaments and to expose the individual filaments to the gaseous compound whereby iron is deposited on the filaments uniformly.

References Cited in the file of this patent UNITED STATES PATENTS 1,072,904 Bontempi Sept. 9, 1913 1,998,060 Seibt Apr. 16, 1935 2,304,182 Lang Dec. 8, 1942 2,325,126 Giesler July 27, 1943 2,344,138 Drummond Mar. 14, 1944 2,428,654 Collins Oct. 7, 1947 2,542,819 Kropa Feb. 20, 1951 2,577,936 Waggoner Dec. 11, 1951 2,584,660 Bancroft Feb. 5, 1952 2,602,033 Lander July 1, 1952 2,616,165 Brennan Nov. 4, 1952 2,622,041 Godley Dec. 16, 1952 2,622,043 Roush Dec. 16, 1952 FOREIGN PATENTS 306,902 Great Britain June 20, 1930 

1. IN A PROCESS OF PLATING GLASS FIBER ROVINGS WITH IRON METAL AS THE SAME IS PASSED THROUGH A PLATING CHAMBER WHICH PROCESS COMPRISES MOVING THE GLASS FIBER IN THE FORM OF UNTWISTED PARALLEL STRANDS INTO A CONFINED ZONE FILLED WITH DRY AIR HEATED TO AT LEAST 150*F., AND THENCE THROUGH A PLATING AREA SURROUNDED BY SAID CONFINED ZONE EXCLUDING OXYGEN AND WATER VAPOR FROM THE PLATING AREA BY FILLING THE SAME WITH DRY INERT GAS, INTRODUCING GASEOUS IRON PENTACARBONYL INTO SAID PLATING AREA TOGETHER WITH SAID INERT GAS A CARRIER, VIBRATING THE ROVING TO CAUSE TEMPORARY SEPARATION OF THE ROVING STRANDS EXPOSING THE SAME TO GASEOUS IRON CARBONYL, AND HEATING THE THUS EXPOSED STRANDS OF GLASS FIBER AT A TEMPERATURE TO CAUSE DECOMPOSITION OF THE IRON CARBONYL AND DEPOSITION OF METALLIC IRON ON THE SURFACE OF THE FIBERS, AND THEREAFTER GRADUALLY COOLING THE RESULTANT IRON-COATED GLASS FIBERS WITHIN SAID CONFINED ZONE. 